1. Field of the Invention
A primer or binder premix of polymer concrete is disclosed that has a solubility parameter which allows high affinity toward other moist polymer concretes and polar substrates during mixing and casting, but becomes virtually insoluble in water after the cure process is complete (after the polymerization). The subject primer or binder premix is utilized in the repair of a bridge, highway, roadway, airport runway, parking structure, patio or like type structure.
2. Description of the Background Art
There are four basic polymer concretes (PCs) which have been used and/or tested extensively for rehabilitation of a common building material known as Portland cement concrete (PCC). Examples are repairs of parking structures, bridges, highways, airport runways, industrial floors, and the like. Usually, the repair work should take a minimum amount of time, preferably less than five hours. The binders for the four basic PCs are epoxies, polyurethanes, methacrylates, and unsaturated polyesters. Each of them has advantages and disadyantages. Epoxies have advantages of being tougher, having low volume shrinkage, and superior bond adhesions. However, they tend to have poor cure characteristics (difficult to control pot-life and curetime over a wide application temperature range). Polyurethanes have many of the good characteristic of epoxies, but also have a poor cure behavior that is similar to epoxies, and have marginal bonding characteristics. Both resins cure through a step-polymerization mechanism, and consequently the overall cure process is difficult to control.
Given the above facts, one common application procedure is by a multilayer overlay method, i.e. applying the resin first and then broadcasting the aggregates over the wet binder, and repeating the process three to five times. Another application method is to prepack the aggregates first and then apply the resin over the aggregates. These methods have the disadvantage of taking a prolonged period of repair work or giving nonuniform compositions of PCs.
Since the other two basic binders, methacrylates and unsaturated polyesters, undergo a cure process by a free-radical chain mechanism, their pot-life and cure processes can be controlled more readily. With these systems a polymer concrete slurry (e.g. binder and aggregates are premixed into a slurry) can be applied in a single step. Methyl methacrylate (MMA) has been utilized in such a slurry. MMA, with its very low viscosity, has a strong advantage of being able to penetrate into fine cracks and pores; however, its high volatility and flammability are strong disadvantages. Recently high molecular weight methacrylates (HMWMs) have been used in place of MMA in order to improve primarily volatility and safety characteristics. Although there are a variety of commercial methacrylates available, their bonding characteristics are marginal (poor bonding to moist surfaces), and some are brittle or expensive.
Unsaturated polyesters have been widely used for overlay work for bridges and roads, but they have poor bonding characteristics to PCC and aggregates, although incorporation of silane coupling agents improves the bonding to a degree. Many overlay works with unsaturated polyesters use HMWM as a primer.
No data on vinyl esters are available for repair work of outdoor concrete structures such as for bridges, highways, and the like, but vinyl esters have been used as chemical resistant overlays for industrial floors (R. A. Schoenberger, et. al. ICPIC Working Papers, Sept. 24-27, 1991).
In general, the currently known PC systems which undergo cure processes by free-radical chain reactions, have either poor or borderline bonding characteristics, especially when the surfaces are moist. Very rigorous drying and good surface preparation of the substrates to be repaired, and aggregates having very low moisture content have been emphasized for the acceptable repair. Common failures of repairs with unsaturated polyester PCs and HMWM PCs occur at the interfacial bonding. The failures are believed to be mainly due to shear stresses that are caused by cure shrinkage and the difference between the thermal expansion coefficient of two solid materials. There are volume shrinkage reducing agents available to minimize the shrinkage during cure. However, debonding can be caused by other factors such as moisture, freezing of water filled PCC, acid rain, oil, heavy wheel loads, deicing salts, tracked-on abrasives such as rocks, snowplow blades, vapor pressure from the substrate, live load shear stresses caused by turning, braking, or accelerating vehicles, impact stresses caused by roughness in the riding surface, and similar conditions. Therefore, it is desirable to develop PCs which give good bonding and have good strain energy, impact strength, and chemical resistance.